Synthetic leather

ABSTRACT

The present invention provides a synthetic leather including at least a base (i), an adhesive layer (ii), and a skin layer (iii). The adhesive layer (ii) is formed of a urethane resin composition including a urethane resin (A) produced using an aromatic polyisocyanate (a1) as a raw material and water (B). The skin layer (iii) is formed of a urethane resin composition including an anionic urethane resin (X) having an anionic group concentration of 0.25 mmol/g or less, water (Y), and an anionic surfactant (Z). The aromatic polyisocyanate (a1) preferably includes toluene diisocyanate. The urethane resin (A) has an aromatic ring concentration of 0.1 to 2.5 mol/kg.

TECHNICAL FIELD

The present invention relates to a synthetic leather.

BACKGROUND ART

Polyurethane resins have been broadly used in the production ofsynthetic leather (including artificial leather) because of their highmechanical strength and good feeling. Although solvent-based urethaneresins including N,N-dimethylformamide (DMF) have been used for use inthe production of synthetic leather in most cases, there has been ademand for using DMF-free urethane resins in the production of thelayers constituting synthetic leather in the context of DMF regulationsin Europe, strengthening of the regulations on VOC emissions in Chinaand Taiwan, DMF regulations in major apparel companies, and the like.

In order to address the above circumstances, a urethane resincomposition that is, for example, an aqueous dispersion of a urethaneresin has been broadly studied (e.g., see PTL 1). While the shift of thematerial for the skin layer of synthetic leather from a solvent-basedurethane resin to a water-based urethane resin has been graduallyincreased in the market as in the invention described in PTL 1, theshift of the urethane resin for the adhesive layer to a water-basedurethane resin has not been done. This is primarily because the peelstrengths of urethane resins provided in the form of an aqueousdispersion or the like are not sufficiently high compared withsolvent-based urethane resins. Moreover, the skin layer has manyproblems to be solved, such as an odor caused by a neutralizer andreduction in the amount of bleeding.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2007-119749

SUMMARY OF INVENTION Technical Problem

An object to be solved by the present invention is to provide asynthetic leather that does not have a strong odor and is excellent interms of peel strength and bleed resistance.

Solution to Problem

The present invention provides a synthetic leather including at least abase (i), an adhesive layer (ii), and a skin layer (iii). The adhesivelayer (ii) is formed of a urethane resin composition including aurethane resin (A) and water (B), the urethane resin (A) being producedusing an aromatic polyisocyanate (a1) as a raw material. The skin layer(iii) is formed of a urethane resin composition including an anionicurethane resin (X) having an anionic group concentration of 0.25 mmol/gor less, water (Y), and an anionic surfactant (Z).

Advantageous Effects of Invention

The synthetic leather according to the present invention does not have astrong odor and is excellent in terms of peel strength and bleedresistance.

In addition, since the adhesive layer (ii) includes the specificurethane resin, the synthetic leather further has excellent hydrolysisresistance in addition to the above-described advantageous effects.

Thus, the synthetic leather according to the present invention may beused in various applications. In particular, the synthetic leatheraccording to the present invention may be used in applications thatrequire high durability, such as automotive interior materials,furniture, and sports shoes, in which it has been considered difficultto use water-based urethane resins instead of solvent-based urethaneresins.

DESCRIPTION OF EMBODIMENTS

The synthetic leather according to the present invention includes atleast a base (i), an adhesive layer (ii), and a skin layer (iii).

It is necessary that the adhesive layer (ii) be formed of a urethaneresin composition that includes a urethane resin (A) produced using anaromatic polyisocyanate (a1) as a raw material and water (B). Adding aurethane resin produced using an aromatic polyisocyanate (a1), which hasa strong intermolecular interaction, as a raw material to the adhesivelayer (ii) enables a markedly high peel strength to be achieved.

The urethane resin (A) can be dispersed in the water (B). Examples ofthe urethane resin (A) include a urethane resin having a hydrophilicgroup, such as an anionic group, a cationic group, or a nonionic group;and a urethane resin forcibly dispersed in the water (B) with anemulsifier. The above urethane resins (A) may be used alone or incombination of two or more.

For producing the urethane resin having an anionic group, for example,one or more compounds selected from the group consisting of compoundshaving a carboxyl group and compounds having a sulfonyl group may beused as a raw material.

Examples of the compounds having a carboxyl group include2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid,2,2-dimethylolbutyric acid, 2,2-dimethylolpropionic acid, and2,2-valeric acid. The above compounds may be used alone or incombination of two or more.

Examples of the compounds having a sulfonyl group include3,4-diaminobutanesulfonic acid, 3,6-diamino-2-toluenesulfonic acid,2,6-diaminobenzenesulfonic acid, N-(2-aminoethyl)-2-aminosulfonic acid,N-(2-aminoethyl)-2-aminoethylsulfonic acid,N-2-aminoethane-2-aminosulfonic acid, and N-(2-aminoethyl)-β-alanine;and salts of the above compounds. The above compounds may be used aloneor in combination of two or more.

A part or the entirety of the carboxyl or sulfonyl groups may beneutralized with a basic compound in the urethane resin composition.Examples of the basic compound include organic amines, such as ammonia,triethylamine, pyridine, and morpholine; alkanolamines, such asmonoethanolamine and dimethylethanolamine; and metal basic compoundsincluding sodium, potassium, lithium, calcium, or the like.

For producing the urethane resin having a cationic group, for example,one or more compounds having an amino group may be used as a rawmaterial.

Examples of the compounds having an amino group include compounds havingprimary and secondary amino groups, such as triethylenetetramine anddiethylenetriamine; and compounds having a tertiary amino group, such asN-alkyldialkanolamine (e.g., N-methyldiethanolamine orN-ethyldiethanolamine) and N-alkyldiaminoalkylamine (e.g.,N-methyldiaminoethylamine or N-ethyldiaminoethylamine). The abovecompounds may be used alone or in combination of two or more.

For producing the urethane resin having a nonionic group, for example,one or more compounds having an oxyethylene structure may be used as araw material.

Examples of the compounds having an oxyethylene structure includepolyether polyols having an oxyethylene structure, such aspolyoxyethylene glycol, polyoxyethylene polyoxypropylene glycol, andpolyoxyethylene polyoxytetramethylene glycol. The above compounds may beused alone or in combination of two or more.

Examples of the emulsifier used for producing the urethane resinforcibly dispersed in the water (B) include nonionic emulsifiers, suchas polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether,polyoxyethylene styryl phenyl ether, polyoxyethylene sorbitoltetraoleate, and a polyoxyethylene-polyoxypropylene copolymer; anionicemulsifiers, such as a fatty acid salt (e.g., sodium oleate), an alkylsulfate ester salt, an alkylbenzene sulfonate salt, an alkylsulfosuccinate salt, a naphthalene sulfonate salt, a polyoxyethylenealkyl sulfate salt, an alkane sulfonate sodium salt, and an alkyldiphenyl ether sulfonic acid sodium salt; and cationic emulsifiers, suchas an alkylamine salt, an alkyltrimethylammonium salt, and analkyldimethylbenzylammonium salt. The above emulsifiers may be usedalone or in combination of two or more.

The urethane resin (A) is preferably the urethane resin having ananionic group in order to further enhance dispersion stability in water,hydrolysis resistance, and lightfastness.

The urethane resin having an anionic group may be, for example, theproduct of reaction of the above-described raw material used forproducing the urethane resin having an anionic group, an aromaticpolyisocyanate (a1), a polyol (a2), and a chain extender (a3) that isoptionally used as needed.

The proportion of the raw material used for producing the urethane resinhaving an anionic group to the polyol (a2) is preferably 0.05% by massor more, is more preferably 0.1% by mass or more, is further preferably0.5% by mass or more, and is particularly preferably 1% by mass or more;is preferably 10% by mass or less, is more preferably 6.2% by mass orless, is further preferably 3% by mass or less, and is particularlypreferably 2.7% by mass or less; and is preferably 0.05% to 10% by mass,is more preferably 0.1% to 6.2% by mass, is further preferably 0.5% to3% by mass, and is particularly preferably 1% to 2.7% by mass, in orderto adjust the anionic group concentration in the urethane resin (A) andthereby further enhance hydrolysis resistance and lightfastness.

The aromatic polyisocyanate (a1), which has strong intermolecularforces, is a component essential for further increasing peel strengthdue to the packing effects. Examples of the aromatic polyisocyanate (a1)include phenylene diisocyanate, toluene diisocyanate, diphenylmethanediisocyanate, naphthalene diisocyanate, polymethylene polyphenylpolyisocyanate, and carbodiimidized diphenylmethane polyisocyanate. Theabove aromatic polyisocyanates may be used alone or in combination oftwo or more. Among the above aromatic polyisocyanates, diphenylmethanediisocyanate and/or toluene diisocyanate is preferably used, and toluenediisocyanate is more preferably used in order to reduce crystallinity toan adequate level and thereby further increase peel strength.

In the case where toluene diisocyanate is used as an aromaticpolyisocyanate (a1), the proportion of toluene diisocyanate to thearomatic polyisocyanate (a1) is preferably 50% by mass or more and ismore preferably 70% by mass or more in order to further increase peelstrength.

The aromatic polyisocyanate (a1) may further include an aliphatic oralicyclic polyisocyanate that does not impair the advantageous effectsof the present invention.

Examples of the aliphatic or alicyclic polyisocyanate include aliphaticand alicyclic polyisocyanates, such as hexamethylene diisocyanate,lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate,dicyclohexylmethane diisocyanate, xylylene diisocyanate,tetramethylxylylene diisocyanate, dimer acid diisocyanate, andnorbornene diisocyanate. The above polyisocyanates may be used alone orin combination of two or more.

Examples of the polyol (a2) include a polyether polyol, a polyesterpolyol, a polycarbonate polyol, a dimer diol, an acrylic polyol, and apolybutadiene polyol. The above polyols may be used alone or incombination of two or more. Among these, a polyether polyol and/or apolycarbonate polyol is preferably used in order to further enhancehydrolysis resistance.

The number-average molecular weight of the polyol (a2) is preferably 500to 10,000 and is more preferably 800 to 5,000 in order to furtherincrease peel strength and the mechanical strength of the coating layerand further enhance hydrolysis resistance. The number-average molecularweight of the polyol (a2) is number-average molecular weight determinedby gel permeation column chromatography (GPC).

The polyol (a2) may be used in combination with a chain extender (a3) (achain extender that does not include any of a carboxyl group and asulfonyl group and has a molecular weight of 50 or more and less than500) as needed. Examples of the chain extender include a chain extenderhaving a hydroxyl group and a chain extender having an amino group. Theabove chain extenders may be used alone or in combination of two ormore. Among these, a chain extender having a hydroxyl group ispreferably used in order to further enhance lightfastness.

Examples of the chain extender having a hydroxyl group include aliphaticpolyols, such as ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,hexamethylene glycol, saccharose, methylene glycol, glycerin, andsorbitol; aromatic polyols, such as bisphenol A, 4,4′-dihydroxydiphenyl,a 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfone,hydrogenated bisphenol A, and hydroquinone; and water. The above chainextenders may be used alone or in combination of two or more. Amongthese, aliphatic polyols are preferably used in order to readily reducediscoloration and further enhance lightfastness.

Examples of the chain extender having an amino group includeethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine,piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine,isophoronediamine, 4,4′-dicyclohexylmethanediamine,3,3′-dimethyl-4,4′-dicyclohexylmethanediamine, 1,2-cyclohexanediamine,1,4-cyclohexanediamine, aminoethylethanolamine, hydrazine,diethylenetriamine, and triethylenetetramine. The above chain extendersmay be used alone or in combination of two or more.

In the case where the chain extender (a3) is used, the amount of thechain extender (a3) used is preferably 0.5% to 40% by mass and is morepreferably 1% to 20% by mass of the total mass of the raw materialsconstituting the urethane resin (A) in order to further enhance thedurability of the coating layer.

For producing the urethane resin (A), for example, the raw material usedfor producing the urethane resin having a hydrophilic group, thearomatic polyisocyanate (a1), the polyol (a2), and the optional chainextender (a3) may be charged to react with one another in one batch.This reaction may be conducted, for example, at 50° C. to 100° C. for 3to 10 hours.

The molar ratio of the isocyanate group included in the aromaticpolyisocyanate (a1) to the total of the hydroxyl and amino groupsincluded in the polyol (a2), the raw material used for producing theurethane resin having a hydrophilic group, and, in the case where thechain extender (a3) is used, the chain extender (a3), that is,[(Isocyanate group)/(Total of hydroxyl and amino groups)], is preferably0.8 to 1.2 and is more preferably 0.9 to 1.1.

It is preferable to deactivate the isocyanate group that remains in theurethane resin (A) in the production of the urethane resin (A). Fordeactivating the isocyanate group, an alcohol having a hydroxyl group,such as methanol, is preferably used. In the case where the alcohol isused, the amount of the alcohol used is preferably 0.001 to 10 parts bymass relative to 100 parts by mass of the urethane resin (A).

An organic solvent may be used in the production of the urethane resin(A). Examples of the organic solvent include ketones, such as acetoneand methyl ethyl ketone; ethers, such as tetrahydrofuran and dioxane;acetate esters, such as ethyl acetate and butyl acetate; nitriles, suchas acetonitrile; and amides, such as dimethylformamide andN-methylpyrrolidone. The above organic solvents may be used alone or incombination of two or more. The organic solvent is preferably removed bydistillation or the like in the production of the urethane resincomposition.

The anionic group concentration in the urethane resin (A) produced bythe above-described method is preferably 0.35 mmol/g or less in order tofurther enhance hydrolysis resistance. Setting the anionic groupconcentration to fall within the above range may limit the degradationof hydrolysis resistance caused by hydrophilic groups while maintainingthe dispersibility of the urethane resin (A) in water and peel strength.The anionic group concentration in the urethane resin (A) is preferably0.01 mmol/g or more and is more preferably 0.01 mmol/g or more; ispreferably 0.25 mmol/g or less and is more preferably 0.22 mmol/g orless; and is preferably 0.005 to 0.25 mmol/g or less and is morepreferably 0.01 to 0.22 mmol/g in order to further enhance hydrolysisresistance. The concentration of an anionic group in the urethane resin(A) is the quotient of the number of moles of the anionic groups derivedfrom the raw material used for producing the urethane resin having ananionic group divided by the total mass of the raw materialsconstituting the urethane resin (A).

The aromatic ring concentration in the urethane resin (A) is preferably0.1 mol/kg or more, is more preferably 0.3 mol/kg or more, and isfurther preferably 0.4 mol/kg or more; is preferably 2.5 mol/kg or less,is more preferably 2 mol/kg or less, and is further preferably 1.5mol/kg or less; and is preferably 0.1 to 2.5 mol/kg, is more preferably0.3 to 2 mol/kg, and is further preferably 0.4 to 1.5 mol/kg in order tofurther increase peel strength. In the above calculation, the molecularweights of benzene and naphthalene that do not include a substituent areused as the molecular weights of aromatic rings.

The weight-average molecular weight of the urethane resin (A) ispreferably 2,000 or more, is more preferably 4,000 or more, and isfurther preferably 6,000 or more; is preferably 150,000 or less, is morepreferably 100,000 or less, and is further preferably 70,000 or less;and is preferably 2,000 to 150,000, is more preferably 4,000 to 100,000,and is further preferably 6,000 to 70,000 in order to further increasepeel strength. The weight-average molecular weight of the urethane resin(A) is weight-average molecular weight determined by gel permeationcolumn chromatography (GPC).

Examples of the water (B) include ion-exchange water, distilled water,and tap water. Among these, ion-exchange water that does not contain alarge amount of impurities is preferably used. The content of the water(B) in the urethane resin composition is preferably 20% to 90% by massand is more preferably 40% to 80% by mass from the viewpoints ofworkability, ease of coating, and preservation stability.

The urethane resin composition used for producing the adhesive layer(ii), which includes the urethane resin (A) and the aqueous medium (B),may optionally include other additives.

Examples of the other additives include a urethanizing catalyst, aneutralizer, a crosslinking agent, a silane coupling agent, a thickener,a filler, a thixotropy-imparting agent, a tackifier, a wax, a heatstabilizer, a light stabilizer, a fluorescent brightening agent, ablowing agent, a pigment, a dye, an electrical conductivity-impartingagent, an antistatic agent, a moisture permeability improver, a waterrepellent, an oil repellent, a hollow foam, a flame retardant, adesiccant, a moisture absorbent, a deodorant, a foam stabilizer, anantiblocking agent, and an antihydrolysis agent. The above additives maybe used alone or in combination of two or more.

It is necessary that the urethane resin composition used for producingthe skin layer (iii) be a urethane resin composition that includes ananionic urethane resin (X) having an anionic group concentration of 0.25mmol/g or less, water (Y), and an anionic surfactant (Z). Setting theanionic group concentration in the urethane resin to fall within theabove range reduces the amount of the amine used, which commonly servesas a neutralizer, and thereby addresses the odor problem. The use of theanionic surfactant (Z) enables the dispersion stability of the urethaneresin in water to be enhanced even when the anionic group concentrationis low. In addition, the anionic group included in the anionicsurfactant (Z) is likely to form a hydrogen bond with the anionic groupincluded in the urethane resin. This reduces the amount of bleeding.

The anionic group concentration in the anionic urethane resin (X) ispreferably 0.005 mmol/g or more and is more preferably 0.01 mmol/g ormore; is preferably 0.25 mmol/g or less and is more preferably 0.2mmol/g or less; and is preferably 0.005 to 0.25 mmol/g and is morepreferably 0.01 to 0.2 mmol/g in order to further reduce the odor whilemaintaining dispersion stability in water. The anionic groupconcentration in the anionic urethane resin (X) is the quotient of thenumber of moles of the anionic groups derived from the raw material usedfor producing the urethane resin having an anionic group divided by thetotal mass of the raw materials constituting the anionic urethane resin(X).

The method for introducing an anionic group into the anionic urethaneresin (X) is the same as for the urethane resin (A).

Specifically, the anionic urethane resin (X) may be, for example, theproduct of reaction of the above-described raw material used forproducing the urethane resin having an anionic group, a polyisocyanate(x1), a polyol (x2), and an extender (x3).

The proportion of the raw material used for producing the urethane resinhaving an anionic group to the polyol (x2) is preferably 0.05% by massor more, is more preferably 0.1% by mass or more, and is furtherpreferably 0.3% by mass or more; is preferably 10% by mass or less, ismore preferably 7% by mass or less, and is further preferably 4% by massor less; and is preferably 0.05% to 10% by mass, is more preferably 0.1%to 7% by mass, and is further preferably 0.3% to 4% by mass in order tofurther enhance chemical resistance.

Examples of the polyisocyanate (x1) include aliphatic and alicyclicpolyisocyanates, such as hexamethylene diisocyanate, lysinediisocyanate, cyclohexane diisocyanate, isophorone diisocyanate,dicyclohexylmethane diisocyanate, xylylene diisocyanate,tetramethylxylylene diisocyanate, dimer acid diisocyanate, andnorbornene diisocyanate; and aromatic polyisocyanates, such as phenylenediisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate,naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, andcarbodiimidized diphenylmethane polyisocyanate. The abovepolyisocyanates may be used alone or in combination of two or more.Among these, one or more polyisocyanates selected from the groupconsisting of isophorone diisocyanate, dicyclohexylmethane diisocyanate,and hexamethylene diisocyanate are more preferably used in order tofurther enhance lightfastness.

Examples of the polyol (x2) include a polyether polyol, a polyesterpolyol, a polycarbonate polyol, a dimer diol, an acrylic polyol, and apolybutadiene polyol. The above polyols may be used alone or incombination of two or more. Among these, a polycarbonate polyol and/or apolyer polyol is preferably used, and a polycarbonate polyol and/or apolypropylene polyol is more preferably used in order to further enhancechemical resistance.

The polycarbonate polyol is preferably a polycarbonate polyol producedusing hexanediol and/or ε-caprolactone as a raw material in order tofurther enhance chemical resistance.

The number-average molecular weight of the polyol (x2) is preferably 500to 100,000 and is more preferably 800 to 10,000 in order to furtherenhance chemical resistance and further increase mechanical strength.The number-average molecular weight of the polyol (x2) is number-averagemolecular weight determined by gel permeation column chromatography(GPC).

Examples of the chain extender (x3) include a chain extender that has ahydroxyl group and a molecular weight of 50 or more and less than 500and a chain extender having an amino group. The above chain extendersmay be used alone or in combination of two or more.

Examples of the chain extender having a hydroxyl group include aliphaticpolyols, such as ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol,hexamethylene glycol, saccharose, methylene glycol, glycerin, andsorbitol; aromatic polyols, such as bisphenol A, 4,4′-dihydroxydiphenyl,a 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfone,hydrogenated bisphenol A, and hydroquinone; and water. The above chainextenders may be used alone or in combination of two or more.

Examples of the chain extender having an amino group includeethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine,piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine,isophoronediamine, 4,4′-dicyclohexylmethanediamine,3,3′-dimethyl-4,4′-dicyclohexylmethanediamine, 1,2-cyclohexanediamine,1,4-cyclohexanediamine, aminoethylethanolamine, hydrazine,diethylenetriamine, triethylenetetramine, and adipic acid dihydrazide.The above chain extenders may be used alone or in combination of two ormore.

The chain extender (x3) is preferably a chain extender having an aminogroup in order to further enhance lightfastness. It is preferable to useone or more chain extenders selected from the group consisting ofethylenediamine, isophoronediamine, and hydrazine.

The amount of the chain extender (x3) used is preferably 0.01% to 20% bymass and is more preferably 0.05% to 10% by mass of the total mass ofthe raw materials constituting the urethane resin (X) in order tofurther enhance the durability of the coating layer, chemicalresistance, and lightfastness.

For producing the urethane resin (X), for example, the reaction of thepolyisocyanate (x1), the raw material used for producing the urethaneresin having an anionic group, and the polyol (x2) is conducted toprepare a urethane prepolymer having an isocyanate group and, after theanionic group has been neutralized, the water (Y) and the chain extender(x3) are added to the urethane prepolymer to cause a reaction. The abovereaction is preferably conducted, for example, at 50° C. to 100° C. for3 to 10 hours.

The molar ratio of the isocyanate group included in the polyisocyanate(x1) to the total of the hydroxyl and amino groups included in the rawmaterial used for producing the urethane resin having a hydrophilicgroup, the polyol (x2), and the chain extender (x3), that is,[(Isocyanate group)/(Hydroxyl and amino groups)], is preferably 0.8 to1.2 and is more preferably 0.9 to 1.1.

The molar ratio of the isocyanate group included in the polyisocyanategroup (x1) to the hydroxyl group included in the raw material used forproducing the urethane resin having an anionic group and the polyol(x2), that is, [NCO/OH], in the production of the urethane prepolymer ispreferably more than 1.5 and 3 or less and is more preferably 1.7 to2.5.

An organic solvent may be used in the production of the urethane resin(X). Examples of the organic solvent include ketones, such as acetoneand methyl ethyl ketone; ethers, such as tetrahydrofuran and dioxane;acetate esters, such as ethyl acetate and butyl acetate; nitriles, suchas acetonitrile; amides, such as dimethylformamide andN-methylpyrrolidone; and film formation assistants, such as dipropyleneglycol dimethyl ether, diethyl diglycol, and diethyl adipate. The aboveorganic solvents may be used alone or in combination of two or more. Theorganic solvent is preferably acetone and/or a film formation assistant.The above organic solvents other than the film formation assistant arepreferably removed by distillation or the like in the production of theurethane resin composition.

The weight-average molecular weight of the anionic urethane resin (X) ispreferably 60,000 or more and is more preferably 100,000 or more; ispreferably 700,000 or less and is more preferably 500,000 or less; andis preferably 60,000 to 700,000 and is more preferably 100,000 to500,000 in order to further enhance lightfastness. The weight-averagemolecular weight of the anionic urethane resin (X) is weight-averagemolecular weight determined by gel permeation column chromatography(GPC).

The water (Y) may be the same as the water (B). The content of the water(Y) in the urethane resin composition is preferably 30% to 90% by massand is more preferably 35% to 80% by mass from the viewpoint ofworkability, ease of coating, and preservation stability.

Examples of the anionic surfactant (Z) include an alkyl sulfosuccinatesalt, an N-acyl amino acid salt, a lactic acid fatty acid ester salt, afatty acid salt, succinylated monoglyceride, diacetyl tartaric acidmonoglyceride, stearic acid tartaric acid ester, stearic acid citricacid ester, monoglyceride citrate, lecithin, lysolecithin, an alkylsulfate salt, a polyoxyethylene alkyl ether sulfate salt, an acylN-methyl taurine salt, fumaric acid stearyl ester sodium, monoglyceridephosphate, and an alkyl ether phosphate ester salt. The above anionicsurfactants may be used alone or in combination of two or more. Amongthese, an alkyl sulfosuccinate salt is preferably used in order tofurther enhance dispersion stability in water and bleed resistance.

Examples of the alkyl sulfosuccinate salt include an alkylsulfosuccinate salt including a linear or branched alkyl group having 1to 16 carbon atoms and preferably having 2 to 14 carbon atoms. Thenumber of the alkyl groups is preferably 1 to 3. Among these, a dioctylsulfosuccinate salt is preferably used in order to further enhancedispersion stability in water and bleed resistance.

Examples of the salt include a sodium salt, a potassium salt, a lithiumsalt, a calcium salt, and an ammonium salt.

The amount of the anionic surfactant (Z) used is preferably 0.01 partsby mass or more and is more preferably 0.1 parts by mass or more; ispreferably 10 parts by mass or less and is more preferably 3 parts bymass or less; and is preferably 0.01 to 10 parts by mass and is morepreferably 0.1 to 3 parts by mass relative to 100 parts by mass of theanionic urethane resin (X) in order to further enhance dispersionstability in water and bleed resistance.

The above urethane resin composition may optionally include additivesother than the anionic urethane resin (X), the water (Y), or the anionicsurfactant (Z).

Examples of the other additives include an emulsifier, a coagulant, aurethanizing catalyst, a silane coupling agent, a filler, athixotropy-imparting agent, a tackifier, a wax, a heat stabilizer, alight stabilizer, a fluorescent brightening agent, a blowing agent, apigment, a dye, an electrical conductivity-imparting agent, anantistatic agent, a moisture permeability improver, a water repellent,an oil repellent, a hollow foam, a flame retardant, a desiccant, amoisture absorbent, a deodorant, a foam stabilizer, an antiblockingagent, an antihydrolysis agent, and a thickener. The above additives maybe used alone or in combination of two or more.

The synthetic leather according to the present invention is describedbelow.

The synthetic leather according to the present invention includes atleast the base (i), the adhesive layer (ii), and the skin layer (iii).Specific examples of the structure of the synthetic leather include thefollowing:

(1) Base (i), adhesive layer (ii), and skin layer (iii)

(2) Base (i), adhesive layer (ii), intermediate layer, and skin layer(iii)

(3) Base (i), porous layer, adhesive layer (ii), and skin layer (iii)

(4) Base (i), porous layer, adhesive layer (ii), intermediate layer, andskin layer (iii)

Examples of the base (i) include a fiber base, such as a nonwovenfabric, woven fabric, or knitted fabric made of a polyester fiber, apolyethylene fiber, a nylon fiber, an acrylic fiber, a polyurethanefiber, an acetate fiber, a rayon fiber, a polylactic acid fiber, cotton,hemp, silk, wool, a glass fiber, a carbon fiber, a mixed fiber made ofthe above fibers, or the like; a base prepared by impregnating the abovenonwoven fabric with a resin, such as a polyurethane resin; a baseprepared by forming a porous layer on the above nonwoven fabric; and aresin base composed of thermoplastic urethane (TPU) or the like.

Examples of the porous layer include a porous layer formed by a knownwet deposition method using a solvent-based urethane resin composition;and a porous layer produced by forming pores in a water-based urethaneresin composition by a known method.

Examples of the material constituting the intermediate layer includeknown water-based urethane resins, solvent-based urethane resins,solvent-free urethane resins, water-based acrylic resins, siliconeresins, polypropylene resins, and polyester resins. The above resins maybe used alone or in combination of two or more.

Optionally, a surface treatment layer may be disposed on the skin layer(iii) in order to, for example, prevent scratching. Examples of thematerial constituting the surface treatment layer include knownwater-based urethane resins, solvent-based urethane resins, solvent-freeurethane resins, water-based acrylic resins, silicone resins,polypropylene resins, and polyester resins. The above resins may be usedalone or in combination of two or more.

The method for producing a synthetic leather having the structure (1)above is described below.

For producing the synthetic leather, for example, a skin layer-formingurethane resin composition is applied to a base that has been subjectedto a releasing treatment, the resulting coating layer is dried andprocessed to form a skin layer (iii), an adhesive layer-forming urethaneresin composition is applied to the skin layer (iii), and the resultingcoating layer is dried to form an adhesive layer (ii), which is thenbonded to the base (i). Alternatively, the adhesive layer (ii) may beformed by applying the adhesive layer-forming urethane resin compositionto the skin layer (iii) and drying the coating layer after the coatinglayer has been bonded to the base (i).

For applying the skin layer-forming and adhesive layer-forming urethaneresin compositions, for example, an applicator, a roll coater, a spraycoater, a T-die coater, a knife coater, and a Comma Coater may be used.

The drying of the urethane resin composition is performed, for example,at 40° C. to 130° C. for 1 to 10 minutes. The thicknesses of theadhesive layer (ii) and the skin layer (iii) are determinedappropriately in accordance with the application in which the syntheticleather is used and are, for example, 0.5 to 100 μm.

Subsequent to the production of the synthetic leather, for example,aging may be performed at 30° C. to 100° C. for 1 to 10 days as needed.

The synthetic leather according to the present invention described abovedoes not have a strong odor and is excellent in terms of peel strengthand bleed resistance. In addition, since the adhesive layer (ii)includes the specific urethane resin, the synthetic leather further hasexcellent hydrolysis resistance in addition to the above-describedadvantageous effects.

Thus, the synthetic leather according to the present invention may beused in various applications. In particular, the synthetic leatheraccording to the present invention may be used in applications thatrequire high durability, such as automotive interior materials,furniture, and sports shoes, in which it has been considered difficultto use water-based urethane resins instead of solvent-based urethaneresins.

EXAMPLES

The present invention is described further in detail with reference toExamples below.

[Synthesis Example 1] Preparation of Adhesive Layer-Forming UrethaneResin (A-1) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen capillary tube, 500 parts by mass ofpolycarbonate diol (“DURANOL T5652” produced by Asahi Kasei ChemicalsCorporation, number-average molecular weight: 2,000), 8 parts by mass of2,2-dimethylolpropionic acid (hereinafter, abbreviated as “DMPA”), and394 parts by mass of methyl ethyl ketone were added in a nitrogenstream. After the above components had been mixed to form a uniformmixture, 68 parts by mass of toluene diisocyanate (hereinafter,abbreviated as “TDI”) was added to the mixture. Then, 0.1 parts by massof dibutyltin dilaurate was added to the mixture. Subsequently, areaction was conducted at 70° C. for about 4 hours. Then, 14 parts bymass of 1,3-butanediol was added to the flask. After a reaction had beenconducted at 70° C. for about 1 hour, the reaction was terminated.Hereby, a methyl ethyl ketone solution of a urethane polymer wasprepared. To the methyl ethyl ketone solution of a urethane polymerprepared by the above-described method, 6 parts by mass of triethylaminewas added in order to neutralize the carboxyl group included in theurethane polymer. Subsequently, 886 parts by mass of ion-exchange waterwas added to the solution. Then, methyl ethyl ketone was removed fromthe solution by distillation under reduced pressure. Hereby, an adhesivelayer-forming urethane resin (A-1) composition (nonvolatile content; 40%by mass, anionic group (carboxyl group, the same applies hereinafter)concentration; 0.11 mmol/g, weight-average molecular weight; 29,000,aromatic ring concentration; 0.67 mol/kg) was prepared.

[Synthesis Example 2] Preparation of Adhesive Layer-Forming UrethaneResin (A-2) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen capillary tube, 500 parts by mass ofpolytetramethylene glycol (number-average molecular weight: 2,000), 3parts by mass of ethylene glycol, 12 parts by mass of DMPA, and 403parts by mass of methyl ethyl ketone were added in a nitrogen stream.After the above components had been mixed to form a uniform mixture, 79parts by mass of TDI was added to the mixture. Then, 0.1 parts by massof dibutyltin dilaurate was added to the mixture. Subsequently, areaction was conducted at 70° C. for about 4 hours. Then, 11 parts bymass of 1,3-BG was added to the flask. After a reaction had beenconducted at 70° C. for about 1 hour, the reaction was terminated.Hereby, a methyl ethyl ketone solution of a urethane polymer wasprepared. To the methyl ethyl ketone solution of a urethane polymerprepared by the above-described method, 9 parts by mass of triethylaminewas added in order to neutralize the carboxyl group included in theurethane polymer. Subsequently, 907 parts by mass of ion-exchange waterwas added to the solution. Then, methyl ethyl ketone was removed fromthe solution by distillation under reduced pressure. Hereby, an adhesivelayer-forming urethane resin (A-2) composition (nonvolatile content; 40%by mass, weight-average molecular weight; 46,000, anionic groupconcentration; 0.15 mmol/g, aromatic ring concentration; 0.75 mol/kg)was prepared.

[Synthesis Example 3] Preparation of Adhesive Layer-Forming UrethaneResin (A-3) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen capillary tube, 500 parts by mass ofpolypropylene glycol (number-average molecular weight: 2,000), 9 partsby mass of 1,4-butanediol, 10 parts by mass of DMPA, and 400 parts bymass of methyl ethyl ketone were added in a nitrogen stream. After theabove components had been mixed to form a uniform mixture, 78 parts bymass of TDI was added to the mixture. Then, 0.1 parts by mass ofdibutyltin dilaurate was added to the mixture. Subsequently, a reactionwas conducted at 70° C. for about 4 hours. Then, 4 parts by mass of1,3-BG was added to the flask. After a reaction had been conducted at70° C. for about 1 hour, the reaction was terminated. Hereby, a methylethyl ketone solution of a urethane polymer was prepared. To the methylethyl ketone solution of a urethane polymer prepared by theabove-described method, 7 parts by mass of N,N-dimethylethanolamine wasadded in order to neutralize the carboxyl group included in the urethanepolymer. Subsequently, 901 parts by mass of ion-exchange water was addedto the solution. Then, methyl ethyl ketone was removed from the solutionby distillation under reduced pressure. Hereby, an adhesivelayer-forming urethane resin (A-3) composition (nonvolatile content; 40%by mass, anionic group concentration; 0.13 mmol/g, weight-averagemolecular weight; 68,000, aromatic ring concentration; 0.74 mol/kg) wasprepared.

[Synthesis Example 4] Preparation of Skin Layer-Forming Urethane Resin(X-1) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen inlet tube, 100 parts by mass ofpolypropylene glycol (number-average molecular weight; 2,000), 100 partsby mass of polypropylene glycol (number-average molecular weight;1,000), 7 parts by mass of DMPA, and 16 parts by mass of dipropyleneglycol dimethyl ether were added in a nitrogen stream. After the abovecomponents had been mixed at 70° C. to form a uniform mixture, 90 partsby mass of isophorone diisocyanate was added to the mixture.Subsequently, a reaction was conducted at 100° C. for about 6 hours.Hereby, a solution of a urethane prepolymer having an isocyanate groupwas prepared (NCO/OH=2.0). To the urethane prepolymer solution, 4.7parts by mass of N,N-dimethylethanolamine was added in order toneutralize the carboxyl group included in the urethane prepolymer.Subsequently, 3 parts by mass of dioctyl sodium sulfosuccinate was addedto the solution. Then, stirring was performed to form a uniform mixture.Subsequently, 575 parts by mass of ion-exchange water was added to themixture. Then, 10 parts by mass of ethylenediamine was added to themixture, and a reaction was conducted. Hereby, a skin layer-formingurethane resin (X-1) composition (nonvolatile content; 35% by mass,anionic group concentration; 0.18 mmol/g) was prepared.

[Synthesis Example 5] Preparation of Skin Layer-Forming Urethane Resin(X-2) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen inlet tube, 100 parts by mass ofpolypropylene glycol (number-average molecular weight; 2,000), 100 partsby mass of polypropylene glycol (number-average molecular weight;1,000), 5.5 parts by mass of DMPA, and 15 parts by mass of dipropyleneglycol dimethyl ether were added in a nitrogen stream. After the abovecomponents had been mixed at 70° C. to form a uniform mixture, 85 partsby mass of isophorone diisocyanate was added to the mixture.Subsequently, a reaction was conducted at 100° C. for about 6 hours.Hereby, a solution of a urethane prepolymer having an isocyanate groupwas prepared (NCO/OH=2.0). To the urethane prepolymer solution, 4.2parts by mass of triethylamine was added in order to neutralize thecarboxyl group included in the urethane prepolymer. Subsequently, 6parts by mass of dioctyl sodium sulfosuccinate was added to thesolution. Then, stirring was performed to form a uniform mixture.Subsequently, 598 parts by mass of ion-exchange water was added to themixture. Then, 26 parts by mass of isophoronediamine was added to themixture, and a reaction was conducted. Hereby, a skin layer-formingurethane resin (X-2) composition (nonvolatile content; 35% by mass,anionic group concentration; 0.14 mmol/g) was prepared.

[Synthesis Example 6] Preparation of Skin Layer-Forming Urethane Resin(X-3) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen inlet tube, 200 parts by mass ofpolycarbonate polyol produced using 1,6-hexanediol as a raw material(number-average molecular weight; 2,000), 6.3 parts by mass of DMPA, and14 parts by mass of dipropylene glycol dimethyl ether were added in anitrogen stream. After the above components had been mixed at 70° C. toform a uniform mixture, 65 parts by mass of isophorone diisocyanate wasadded to the mixture. Subsequently, a reaction was conducted at 100° C.for about 6 hours. Hereby, a solution of a urethane prepolymer having anisocyanate group was prepared (NCO/OH=2.0). To the urethane prepolymersolution, 5.5 parts by mass of N,N-diethylethanolamine was added inorder to neutralize the carboxyl group included in the urethaneprepolymer. Subsequently, 3 parts by mass of dioctyl sodiumsulfosuccinate was added to the mixture. Then, stirring was performed toform a uniform mixture. Subsequently, 523 parts by mass of ion-exchangewater was added to the mixture. Then, 7 parts by mass of 80 mass %hydrazine hydrate was added to the mixture, and a reaction wasconducted. Hereby, a skin layer-forming urethane resin (X-3) composition(nonvolatile content; 35% by mass, anionic group concentration; 0.17mmol/g) was prepared.

[Synthesis Example 7] Preparation of Skin Layer-Forming Urethane Resin(X-4) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen inlet tube, 100 parts by mass ofpolypropylene glycol (number-average molecular weight; 2,000), 100 partsby mass of polypropylene glycol (number-average molecular weight;1,000), and 8 parts by mass of DMPA were added in a nitrogen stream.After the above components had been mixed at 70° C. to form a uniformmixture, 93 parts by mass of isophorone diisocyanate was added to themixture. Subsequently, a reaction was conducted at 100° C. for about 6hours. Hereby, a urethane prepolymer having an isocyanate group wasprepared (NCO/OH=2.0). After the urethane prepolymer had been cooled to60° C., 129 parts by mass of acetone was added to the urethaneprepolymer to form a uniform solution. To the urethane prepolymersolution, 6 parts by mass of triethylamine was added in order toneutralize the carboxyl group included in the urethane prepolymer.Subsequently, 2 parts by mass of dioctyl sodium sulfosuccinate was addedto the solution. Then, stirring was performed to form a uniform mixture.Subsequently, 581 parts by mass of ion-exchange water was added to themixture. Then, 10 parts by mass of 80 mass % hydrazine hydrate was addedto the mixture, and a reaction was conducted. After the reaction hadbeen completed, acetone was removed from the mixture by distillationunder reduced pressure. Hereby, a skin layer-forming urethane resin(X-4) composition (nonvolatile content; 35% by mass, anionic groupconcentration; 0.20 mmol/g) was prepared.

[Comparative Synthesis Example 1] Preparation of Adhesive Layer-FormingUrethane Resin (AR-1) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen capillary tube, 500 parts by mass ofpolytetramethylene glycol (number-average molecular weight: 1,000), 15parts by mass of DMPA, and 450 parts by mass of methyl ethyl ketone wereadded in a nitrogen stream. After the above components had been mixed toform a uniform mixture, 149 parts by mass of isophorone diisocyanate(IPDI) was added to the mixture. Then, 0.1 parts by mass of dibutyltindilaurate was added to the mixture. Subsequently, a reaction wasconducted at 70° C. for about 4 hours. Then, 11 parts by mass of1,3-butanediol was added to the flask. A reaction was conducted at 70°C. for 1 hour. Hereby, a methyl ethyl ketone solution of a urethaneprepolymer was prepared. To the methyl ethyl ketone solution of aurethane polymer prepared by the above-described method, 10 parts bymass of N,N-dimethylethanolamine was added in order to neutralize thecarboxyl group included in the urethane polymer. Subsequently, 1,012parts by mass of ion-exchange water was added to the solution. After areaction had been completed, methyl ethyl ketone was removed from thesolution by distillation under reduced pressure. Hereby, an adhesivelayer-forming urethane resin (AR-1) composition (nonvolatile content;40% by mass, anionic group concentration; 0.16 mmol/g, weight-averagemolecular weight; 28,000, aromatic ring concentration; 0 mol/kg) wasprepared.

[Comparative Synthesis Example 2] Preparation of Skin Layer-FormingUrethane Resin (XR-1) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen inlet tube, 100 parts by mass ofpolypropylene glycol (number-average molecular weight; 2,000), 100 partsby mass of polypropylene glycol (number-average molecular weight;1,000), and 20 parts by mass of DMPA were added in a nitrogen stream.After the above components had been mixed at 70° C. to form a uniformmixture, 133 parts by mass of isophorone diisocyanate was added to themixture. Subsequently, a reaction was conducted at 100° C. for about 6hours. Hereby, a urethane prepolymer having an isocyanate group wasprepared (NCO/OH=2.0). After the urethane prepolymer had been cooled to60° C., 151 parts by mass of acetone was added to the urethaneprepolymer to form a uniform solution. To the urethane prepolymersolution, 15 parts by mass of triethylamine was added in order toneutralize the carboxyl group included in the urethane prepolymer.Subsequently, 2 parts by mass of dioctyl sodium sulfosuccinate was addedto the solution. Then, stirring was performed to form a uniform mixture.Subsequently, 683 parts by mass of ion-exchange water was added to themixture. Then, 15 parts by mass of 80 mass % hydrazine hydrate was addedto the mixture, and a reaction was conducted. After the reaction hadbeen completed, acetone was removed from the mixture by distillationunder reduced pressure. Hereby, a skin layer-forming urethane resin(XR-1) composition (nonvolatile content; 35% by mass, anionic groupconcentration; 0.42 mmol/g) was prepared.

[Comparative Synthesis Example 3] Preparation of Skin Layer-FormingUrethane Resin (XR-2) Composition

To a four-necked flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen inlet tube, 100 parts by mass ofpolypropylene glycol (number-average molecular weight; 2,000), 100 partsby mass of polypropylene glycol (number-average molecular weight;1,000), and 8 parts by mass of DMPA were added in a nitrogen stream.After the above components had been mixed at 70° C. to form a uniformmixture, 93 parts by mass of isophorone diisocyanate was added to themixture. Subsequently, a reaction was conducted at 100° C. for about 6hours. Hereby, a urethane prepolymer having an isocyanate group wasprepared (NCO/OH=2.0). After the urethane prepolymer had been cooled to60° C., 129 parts by mass of acetone was added to the urethaneprepolymer to form a uniform solution. To the urethane prepolymersolution, 6 parts by mass of triethylamine was added in order toneutralize the carboxyl group included in the urethane prepolymer.Subsequently, 2 parts by mass of a nonionic surfactant (“Adeka PluronicF-68” produced by ADEKA CORPORATION, hereinafter, abbreviated as“nonionic”) was added to the solution. Then, stirring was performed toform a uniform mixture. Subsequently, 681 parts by mass of ion-exchangewater was added to the mixture. Then, 10 parts by mass of 80 mass %hydrazine hydrate was added to the mixture, and a reaction wasconducted. After the reaction had been completed, acetone was removedfrom the mixture by distillation under reduced pressure. Hereby, a skinlayer-forming urethane resin (XR-2) composition (nonvolatile content;35% by mass, anionic group concentration; 0.20 mmol/g) was prepared.

[Example 1]<Production of Synthetic Leather>

A liquid mixture of 100 parts by mass of the skin layer-forming urethaneresin (X-1) composition prepared in Synthesis example 4, 10 parts bymass of a water-dispersible black pigment (“DILAC HS-9530” produced byDIC Corporation), and 1 part by mass of an associative thickener(“HYDRAN ASSISTER T10” produced by DIC Corporation) was applied to aflat release paper sheet (“DN-TP-155T” produced by Ajinomoto Co., Inc.)so as to form a coating layer having a thickness of 30 μm after beingdried. The coating layer was dried at 70° C. for 2 minutes and at 120°C. for another 2 minutes.

Then, a liquid mixture of 100 parts by mass of the adhesivelayer-forming urethane resin (A-1) composition prepared in Synthesisexample 1, 1 part by mass of an associative thickener (“HYDRAN ASSISTERT10” produced by DIC Corporation), and 9 parts by mass of apolyisocyanate crosslinking agent (“HYDRAN ASSISTER C5” produced by DICCorporation) was applied thereto so as to form a coating layer having athickness of 50 μm after being dried. The coating layer was dried at 70°C. for 3 minutes. Immediately after the coating layer had been dried, anonwoven fabric impregnated with polyurethane was bonded to the driedcoating layer. Subsequently, a heat treatment was performed at 120° C.for 2 minutes. After aging had been performed at 50° C. for 2 days, therelease paper sheet was removed. Hereby, a synthetic leather wasprepared.

Examples 2 to 8 and Comparative Examples 1 to 5

A synthetic leather was prepared as in Example 1, except that the typesof the skin layer-forming urethane resin composition used and theadhesive layer-forming urethane resin composition used were changed asdescribed in Tables 1 to 3.

[Methods for Measuring Number-Average Molecular Weight andWeight-Average Molecular Weight]

The number-average molecular weights of the polyols used in Synthesisexamples above and the important average molecular weights of theurethane resins used in Synthesis examples above are the values measuredby gel permeation column chromatography (GPC) under the followingconditions.

Measuring equipment: High-speed GPC equipment (“HLC-8220GPC” produced byTosoh Corporation)

Columns: the following columns produced by Tosoh Corporation wereconnected to one another in series.

“TSKgel G5000” (7.8 mm I.D.×30 cm)×1

“TSKgel G4000” (7.8 mm I.D.×30 cm)×1

“TSKgel G3000” (7.8 mm I.D.×30 cm)×1

“TSKgel G2000” (7.8 mm I.D.×30 cm)×1

Detector: RI (differential refractometer)

Column temperature: 40° C.

Eluent: Tetrahydrofuran (THF)

Flow rate: 1.0 mL/min

Injection volume: 100 μL (tetrahydrofuran solution having a sampleconcentration of 0.4 mass %)

Reference samples: A calibration curve was prepared using the followingstandard polystyrenes.

(Standard Polystyrenes)

“TSKgel standard polystyrene A-500” produced by Tosoh Corporation

“TSKgel standard polystyrene A-1000” produced by Tosoh Corporation

“TSKgel standard polystyrene A-2500” produced by Tosoh Corporation

“TSKgel standard polystyrene A-5000” produced by Tosoh Corporation

“TSKgel standard polystyrene F-1” produced by Tosoh Corporation

“TSKgel standard polystyrene F-2” produced by Tosoh Corporation

“TSKgel standard polystyrene F-4” produced by Tosoh Corporation

“TSKgel standard polystyrene F-10” produced by Tosoh Corporation

“TSKgel standard polystyrene F-20” produced by Tosoh Corporation

“TSKgel standard polystyrene F-40” produced by Tosoh Corporation

“TSKgel standard polystyrene F-80” produced by Tosoh Corporation

“TSKgel standard polystyrene F-128” produced by Tosoh Corporation

“TSKgel standard polystyrene F-288” produced by Tosoh Corporation

“TSKgel standard polystyrene F-550” produced by Tosoh Corporation

[Method for Evaluating Odor]

Each of the synthetic leathers prepared in Examples and Comparativeexamples was charged into a closed container, which was then left tostand at 80° C. for 24 hours. Subsequently, the lid was opened, and anodor was confirmed. An evaluation was made in the following manner.

“A”; No odor was felt.

“B”; A slight odor was felt.

“C”; A strong odor was felt.

[Method for Measuring Peel Strength]

Each of the synthetic leathers prepared in Examples and Comparativeexamples was subjected to Shimadzu Autograph “AG-1” (produced byShimadzu Corporation) to measure peel strength at a full scale of 5 kgand a head speed of 20 mm/min. An evaluation was made in the followingmanner.

“A”; 0.15 MPa or more

“B”; 0.1 MPa or more and less than 0.15 MPa

“C”; Less than 0.1 MPa

[Method for Evaluating Bleed Resistance]

Each of the synthetic leathers prepared in Examples and Comparativeexamples was left to stand at 70° C. and a humidity of 95% for 5 weeksand, subsequently, the appearance of the synthetic leather wasinspected. An evaluation was made in the following manner.

“A”; No abnormality was observed in appearance.

“B”; A slight amount of bleeding was observed on the surface.

“C”; A large amount of bleeding was observed on the surface.

[Method for Evaluating Hydrolysis Resistance]

Each of the synthetic leathers prepared in Examples and Comparativeexamples was left to stand at 70° C. and a humidity of 95% for 5 weeksand, subsequently, the appearance of the synthetic leather wasinspected. Furthermore, the synthetic leather was touched by fingers. Anevaluation was made in the following manner.

“A”; No abnormality was observed in appearance or when touched byfingers.

“B”; Gloss was changed in appearance, but no abnormality was observedwhen touched by fingers.

“C”; Gloss was changed in appearance, and stickiness was confirmed.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Adhesive layer Type ofadhesive (A-1) (A-2) (A-3) (A-1) (ii) layer-forming urethane resincomposition Type of TDI TDI TDI TDI polyisocyanate Anionic group 0.110.15 0.13 0.11 concentration in urethane resin (A) (mmol/g) Aromaticring 0.67 0.75 0.74 0.67 concentration in urethane resin (A) (mol/kg)Weight-average 29,000 46,000 68,000 29,000 molecular weight of urethaneresin (A) Skin layer Type of skin (X-1) (X-1) (X-1) (X-2) (iii)layer-forming urethane resin composition Anionic group 0.18 0.18 0.180.14 concentration in urethane resin (X) (mmol/g) Anionic SDS SDS SDSSDS surfactant (Z) Odor evaluation A A A A Peel strength evaluation A AA A Bleed resistance A A A A evaluation Hydrolysis resistance A A A Aevaluation

TABLE 2 Example 5 Example 6 Example 7 Example 8 Adhesive Type ofadhesive (A-2) (A-1) (A-3) (A-1) layer (ii) layer-forming urethane resincomposition Type of TDI TDI TDI TDI polyisocyanate Anionic group 0.150.11 0.13 0.11 concentration in urethane resin (A) (mmol/g) Aromaticring 0.75 0.67 0.74 0.67 concentration in urethane resin (A) (mol/kg)Weight-average 46,000 29,000 68,000 29,000 molecular weight of urethaneresin (A) Skin Type of skin (X-2) (X-3) (X-3) (X-4) layer (iii)layer-forming urethane resin composition Anionic group 0.14 0.17 0.170.2 concentration in urethane resin (X) (mmol/g) Anionic SDS SDS SDS SDSsurfactant (Z) Odor evaluation A A A A Peel strength evaluation A A A ABleed resistance A A A A evaluation Hydrolysis resistance A A A Aevaluation

TABLE 3 Comparative Comparative Comparative Comparative Comparativeexample 1 example 2 example 3 example 4 example 5 Adhesive Type ofadhesive (AR-1) (AR-1) (A-1) (A-1) (AR-1) layer (ii) layer-formingurethane resin composition Type of IPDI IPDI TDI TDI IPDI polyisocyanateAnionic group 0.16 0.16 0.11 0.11 0.16 concentration in urethane resin(A) (mmol/g) Aromatic ring 0 0 0.67 0.67 0 concentration in urethaneresin (A) (mol/kg) Weight-average 28,000 28,000 29,000 29,000 28,000molecular weight of urethane resin (A) Skin Type of skin layer- (XR-1)(XR-2) (XR-1) (XR-2) (X-1) layer (iii) forming urethane resincomposition Anionic group 0.42 0.2 0.42 0.2 0.18 concentration inurethane resin (X) (mmol/g) Surfactant SDS Nonionic SDS Nonionic SDSOdor evaluation C A C A A Peel strength evaluation C C A A C Bleedresistance evaluation A C A C A Hydrolysis resistance C B C A Bevaluation

The abbreviation “SDS” used in Tables 1 and 2 stands for dioctyl sodiumsulfosuccinate.

The results obtained in Examples 1 to 7 confirm that the syntheticleather according to the present invention does not have a strong odorand is excellent in terms of peel strength, bleed resistance, andhydrolysis resistance.

In contrast, in Comparative example 1, where the adhesive layer (ii) didnot include the urethane resin prepared using an aromatic polyisocyanateas a raw material and the skin layer (iii) included a urethane resinhaving an anionic group concentration that was above the range specifiedin the present invention, the synthetic leather had an odor and wasevaluated as poor in terms of peel strength and hydrolysis resistance.

In Comparative example 2, where the adhesive layer (ii) did not includethe urethane resin prepared using an aromatic polyisocyanate as a rawmaterial and the skin layer (iii) included a nonionic surfactant insteadof the anionic surfactant (Z), the synthetic leather was evaluated aspoor in terms of peel strength and bleed resistance.

In Comparative example 3, where the skin layer (iii) included a urethaneresin having an anionic group concentration that was above the rangespecified in the present invention, the synthetic leather had an odorand was evaluated as poor in terms of hydrolysis resistance.

In Comparative example 4, where the skin layer (iii) included a nonionicsurfactant instead of the anionic surfactant (Z), the synthetic leatherwas evaluated as poor in terms of bleed resistance.

In Comparative example 5, where the adhesive layer (ii) was formed usinga urethane resin composition that did not include the urethane resinprepared using an aromatic polyisocyanate as a raw material, thesynthetic leather was evaluated as poor in terms of peel strength.

1. A synthetic leather comprising at least a base (i), an adhesive layer(ii), and a skin layer (iii), the adhesive layer (ii) being formed of aurethane resin composition including a urethane resin (A) and water (B),the urethane resin (A) being produced using an aromatic polyisocyanate(a1) as a raw material, the skin layer (iii) being formed of a urethaneresin composition including an anionic urethane resin (X) having ananionic group concentration of 0.25 mmol/g or less, water (Y), and ananionic surfactant (Z).
 2. The synthetic leather according to claim 1,wherein the aromatic polyisocyanate (a1) includes toluene diisocyanate.3. The synthetic leather according to claim 1, wherein the urethaneresin (A) has an aromatic ring concentration of 0.1 to 2.5 mol/kg. 4.The synthetic leather according to claim 1, wherein the urethane resin(A) has a weight-average molecular weight of 2,000 to 150,000.
 5. Thesynthetic leather according to claim 1, wherein the anionic surfactant(Z) is an alkyl sulfosuccinate salt.
 6. The synthetic leather accordingto claim 2, wherein the urethane resin (A) has an aromatic ringconcentration of 0.1 to 2.5 mol/kg.
 7. The synthetic leather accordingto claim 2, wherein the urethane resin (A) has a weight-averagemolecular weight of 2,000 to 150,000.
 8. The synthetic leather accordingto claim 3, wherein the urethane resin (A) has a weight-averagemolecular weight of 2,000 to 150,000.
 9. The synthetic leather accordingto claim 6, wherein the urethane resin (A) has a weight-averagemolecular weight of 2,000 to 150,000.
 10. The synthetic leatheraccording to claim 2, wherein the anionic surfactant (Z) is an alkylsulfosuccinate salt.
 11. The synthetic leather according to claim 3,wherein the anionic surfactant (Z) is an alkyl sulfosuccinate salt. 12.The synthetic leather according to claim 4, wherein the anionicsurfactant (Z) is an alkyl sulfosuccinate salt.
 13. The syntheticleather according to claim 6, wherein the anionic surfactant (Z) is analkyl sulfosuccinate salt.
 14. The synthetic leather according to claim7, wherein the anionic surfactant (Z) is an alkyl sulfosuccinate salt.15. The synthetic leather according to claim 8, wherein the anionicsurfactant (Z) is an alkyl sulfosuccinate salt.
 16. The syntheticleather according to claim 9, wherein the anionic surfactant (Z) is analkyl sulfosuccinate salt.